[music-dsp] Envelope Detection and Hilbert Transform

Angelo Farina farina at pcfarina.eng.unipr.it
Thu Sep 23 02:57:07 EDT 2004


????
The (real) FFT of a real signal does not produce any "negative frequency"
spectrum, it only produces N/2+1 positive frequency spectral lines....
Or are You doing a complex FFT on a real signal? This is really stupid, it
takes more than twice the computational power required for a real FFT...
Bye!

Angelo Farina
 

> -----Original Message-----
> From: music-dsp-bounces at ceait.calarts.edu 
> [mailto:music-dsp-bounces at ceait.calarts.edu] On Behalf Of 
> Erik de Castro Lopo
> Sent: 23 September 2004 00:10
> To: a list for musical digital signal processing
> Subject: Re: [music-dsp] Envelope Detection and Hilbert Transform
> 
> On Wed, 22 Sep 2004 14:56:12 -0700
> "Joshua Scholar" <joshscholar at yahoo.com> wrote:
> 
> > 
> > All this talk about windows, does that mean you have a way 
> to use FFTs 
> > to do Hilbert Transforms __other__ than convolution?
> 
> Yes, take the FFT of a signal, which creates a N frequency 
> domain samples, with the up half of the being a reflection of 
> the lower half. Zero out the upper half, do an inverse FFT 
> and viola, you have the analytic version of the original 
> signal (ie its Hilbert transform).
> 
> Erik
> -- 
> +-----------------------------------------------------------+
>   Erik de Castro Lopo  nospam at mega-nerd.com (Yes it's valid)
> +-----------------------------------------------------------+
> The National Multiple Sclerosis Society of America recently 
> started an advertising campaign with the slogan "MS: It's not 
> a software company".
> 
> Seasoned IT professionals will have no trouble telling the 
> two MS's apart. One is a debilitating and surprisingly 
> widespread affliction that renders the sufferer barely able 
> to perform the simplest task.
> The other is a disease.
> --
> dupswapdrop -- the music-dsp mailing list and website: 
> subscription info, FAQ, source code archive, list archive, 
> book reviews, dsp links http://shoko.calarts.edu/musicdsp 
> http://ceait.calarts.edu/mailman/listinfo/music-dsp
> 
> 





More information about the music-dsp mailing list